Alternative Power sources - Battery Boxes...What One Company Designed

Author

Battery Boxes...What One Company Designed

Too_Many_Tools

2005-09-16, 5:21 pm

Since I am starting the homepower/automated house journey, I have been
collecting surplus commercial equipment that might prove useful. One of
those items was a surplus Best battery box for a large UPS. Some
comments on the construction and design follows.

The box is designed for sealed 6v batteries (two banks or four) with
the second bank located above the first. The cabinet is metal with
galvenized trays for the batteries to sit in. The box was wired for 12v
at 200 amp with commercial welding cable. There are two in line fuses,
one per bank. The cabinet is on wheels. The cabinet has two vents
located on the back of the cabinet, one lower and one higher. The
cabinet is NOT actively ventilated but relies on natural convection. On
the front it has a single heavy duty switch to switch the direct
current. The switch has a ceramic resistor on it (to quench arcs when
switching?).

Several things caught my attention. The use of metal throughout the
box...I would have expected fiberglass or plastic for corrosion
resistance. Next was the absense of an active ventilation system.
Third, the lack of an integrated charger for the battery box. I assume
the batteries are charged through the UPS.

I plan on making some mods to this box for my home system.

One is to make plastic tray inserts to keep acid at bay.

Next is an active ventilation system.

Third is to consider doing some type of a sliding tray on the bottom
level to allow one to access the batteries easier during maintainance.

Fourth is to incorporate a charging system.

Fifth is to place meters on the front to monitor voltage and amperage
and add the option for remote sensing.

Sixth rewire it for a different voltage (it was 12v at 200a)...any
suggestions?

I would be interested in any suggestions or comments as to what you
have added to or wish you had designed into your system.

Thanks for any and all suggestions.

TMT

Marc F Hult

2005-09-16, 5:21 pm

On 16 Sep 2005 12:23:51 -0700, "Too_Many_Tools" <too_many_tools@yahoo.com>
wrote in message <1126898631.801389.317530@f14g2000cwb.googlegroups.com>:

>Since I am starting the homepower/automated house journey, I have been
>collecting surplus commercial equipment that might prove useful. One of
>those items was a surplus Best battery box for a large UPS. Some
>comments on the construction and design follows.
>
>The box is designed for sealed 6v batteries (two banks or four) with
>the second bank located above the first. The cabinet is metal with
>galvenized trays for the batteries to sit in. The box was wired for 12v
>at 200 amp with commercial welding cable. There are two in line fuses,
>one per bank. The cabinet is on wheels. The cabinet has two vents
>located on the back of the cabinet, one lower and one higher. The
>cabinet is NOT actively ventilated but relies on natural convection. On
>the front it has a single heavy duty switch to switch the direct
>current. The switch has a ceramic resistor on it (to quench arcs when
>switching?).
>
>Several things caught my attention. The use of metal throughout the
>box...I would have expected fiberglass or plastic for corrosion
>resistance. Next was the absense of an active ventilation system.
>Third, the lack of an integrated charger for the battery box. I assume
>the batteries are charged through the UPS.
>
>I plan on making some mods to this box for my home system.
>
>One is to make plastic tray inserts to keep acid at bay.
>
>Next is an active ventilation system.
>
>Third is to consider doing some type of a sliding tray on the bottom
>level to allow one to access the batteries easier during maintainance.
>
>Fourth is to incorporate a charging system.
>
>Fifth is to place meters on the front to monitor voltage and amperage
>and add the option for remote sensing.
>
>Sixth rewire it for a different voltage (it was 12v at 200a)...any
>suggestions?
>
>I would be interested in any suggestions or comments as to what you
>have added to or wish you had designed into your system.
>
>Thanks for any and all suggestions.
>
>TMT

Assuming that you are in US:

Check the National Electrical Code (NEC) which addresses both batteries and
low voltage.

Make sure that the DC/charging system is isolated from the AC, draws not more
than 20 (IIRC) amps source AC, is UL-listed and is not connected to earth
ground.

Above 30 volts, or if the system is not isolated, the NEC is more restrictive.

(FWIW, I have some of your questions. I have a growing 28vdc system.
A natural gas-powered 28VDC generator awaits installation. )

Marc
Marc_F_Hult
www.ECOntrol.org

John Beardmore

2005-09-16, 6:21 pm

In message <1126898631.801389.317530@f14g2000cwb.googlegroups.com>,
Too_Many_Tools <too_many_tools@yahoo.com> writes

>Sixth rewire it for a different voltage (it was 12v at 200a)...any
>suggestions?

How should we know ? Did you have any particular load in mind ?

>I would be interested in any suggestions or comments as to what you
>have added to or wish you had designed into your system.

I suspect most of us select components and design systems in response to
some particular need or requirement.

>Thanks for any and all suggestions.

You seem to be coming at this the way a sculptor approaches a block of
marble.

You sound like you've found an interesting item, that requires a total
overhaul to be made stunningly excellent, to greatly exceed the spec
required to meet some undefined purpose.

What are you actually wanting to achieve ?

Cheers, J/.
--
John Beardmore

MFHult@nothydrologistnot.com

2005-09-16, 6:21 pm

On Fri, 16 Sep 2005 21:22:54 +0100, John Beardmore <wookie@wookie.demon.co.uk>
wrote in message <PF08b26emyKDFwG0@wookie.demon.co.uk>:

>In message <1126898631.801389.317530@f14g2000cwb.googlegroups.com>,
>Too_Many_Tools <too_many_tools@yahoo.com> writes

>You seem to be coming at this the way a sculptor approaches a block of
>marble.
>
>You sound like you've found an interesting item, that requires a total
>overhaul to be made stunningly excellent, to greatly exceed the spec
>required to meet some undefined purpose.
>
>What are you actually wanting to achieve ?
>
>
>Cheers, J/.

My sons call this a " hood ornament project" Finding a neat hood ornament,
they say, I would be inclined to build a car under it...

I can't answer for the original poster, but some projects, especially DIY home
automation projects, can be driven by what one can do rather than what needs to
be achieved. That's often OK.

(Ooops... I jist realized how cross-posted this thread is . Oh well)

A common constellation of reasons that do have specific, useful and attainable
objectives (which also happen to be mine) is to provide a power system that
provide:

1) protection of devices in the home/office/farm/cabin that contain
semiconductors and so may be damaged by lightning and possibly other power-line
disturbances

2) a useful amount of back-up power for lighting, electronic, and other
electrical equipment devices that are needed in emergencies

3) some personal outlet for frustration over 'energy dependence' in all its
contexts.

Gotta go! -- Lightning and thunder as I type this ;-)

.... Marc
Marc_F_Hult
www.ECOntrol.org

Too_Many_Tools

2005-09-16, 8:21 pm

Thanks for the responses so far...

In answer to some of the questions, I could use the battery box just
the way it is.

There is no corrosion to the box and all the parts, cables and such are
there and all functional.

FWIW....I tend to be someone who tries to make something better than it
was. The mods I have mentioned are ones that can be done with little
effort.

I will be using it for emergency power backup with an eye towards
alternative power generation as this project evolves.

As for voltages, since I don't have a alternative ppwer system I am
open to what voltage the battery box will be wired for. From what I
see, it seems that the voltages that alternative home power (AHP) is
using is slowly creeping up. The battery box holds eight batterys...6v
or 12v...so there is a range of voltages that can be used. As it was
wired, it was for 12v at 200amps.

Again, any suggestions are welcomed.

TMT....already looking for that next hood ornament ;< )

John Beardmore

2005-09-16, 8:21 pm

In message <a8dmi11l9vhll42ve5kb5makc4kv3q2gg3@4ax.com>,
MFHult@nothydrologistnot.com writes

>My sons call this a " hood ornament project" Finding a neat hood ornament,
>they say, I would be inclined to build a car under it...
>
>I can't answer for the original poster, but some projects, especially DIY home
>automation projects, can be driven by what one can do rather than what needs to
>be achieved. That's often OK.

Yes - I've got no problem with that, but asking us what voltage to wire
the bank to seems silly. Likely to be determined by available cable
lengths and thicknesses, surplus or cheap inverters etc...

Cheers, J/.
--
John Beardmore

Too_Many_Tools

2005-09-16, 8:21 pm

I ask what voltage because I can wire it in different arrangments...it
was wired for 12v.

I am asking because as you point out there are different inverters out
there.

I have a number of surplus UPS inverters that I may use...I am still in
the design stage on this subject.

The APC Smart/Matrix UPSes are sine wave, are CHEAP and large enough to
be worth using. The downside is that UPS inverters usually have higher
idle current requirements that dedicated inverters available on the
market now. I have yet to do the tradeoffs with a market survey. Any
suggestions you can offer will be appreciated.

TMT

John Beardmore

2005-09-17, 8:21 am

In message <1126911322.406213.125620@o13g2000cwo.googlegroups.com>,
Too_Many_Tools <too_many_tools@yahoo.com> writes

>I ask what voltage because I can wire it in different arrangments...it
>was wired for 12v.
>
>I am asking because as you point out there are different inverters out
>there.

But only you know what they cost YOU.

Personally I have done a lot of mobile stuff on 24 volts because that's
what trucks use. I don't like 12 because the current requires huge
wires, though I've done a bit of that. If it was for home / stationary
use I'd expect to see some efficiency advantages by going to higher
voltages, but if you charge from PV for example, will you be able to get
say a 96V OPT regulator off the shelf ? And what if one battery or PV
in a string fails ? Probability goes up as strings get longer. Lots to
consider.

>I have a number of surplus UPS inverters that I may use...I am still in
>the design stage on this subject.

Good...

>The APC Smart/Matrix UPSes are sine wave, are CHEAP and large enough to
>be worth using. The downside is that UPS inverters usually have higher
>idle current requirements that dedicated inverters available on the
>market now. I have yet to do the tradeoffs with a market survey. Any
>suggestions you can offer will be appreciated.

None really. The inverters we have used have been cheap, modern, fairly
efficient, fragile, small, switching technology, square wave out and
nasty, or have been hugely heavy, inefficient thyristor fired 50Hz 1960s
technology with massive transformers and sin wave output. All down to
what has come out way.

We also have a huge, and I suspect fairly inefficient 7kW UPS inverter
lurking around but there isn't much point in telling you about that.
One day it will come in handy though.

But given the price of modern inverters, is it worth your just going out
and buying what you need when you know what you need ?

Cheers, J/.
--
John Beardmore

Too_Many_Tools

2005-09-17, 12:21 pm

I think that is the path I may take...in the past I have found that
since the electronics continue to get "better" it is usually not worth
trying to design in old stuff....and sometimes "old" means just a few
years old.

My cost for the UPS equipment I am able to find is nil but one needs to
factor in long time power usage (idle current), ability to replace it
when it fails and suitability for the home enviroment. It is a fool who
designs a system around a surplus component that when it fails, you
have to toss the whole system. This battery box in question is a
component that can be useful as my system evolves as it will.

This is one reason for the question of "what voltage" since it is
apparent that the trend is to different voltages than in the past.

TMT

Steve Spence

2005-09-17, 12:21 pm

Too_Many_Tools wrote:

>
> This is one reason for the question of "what voltage" since it is
> apparent that the trend is to different voltages than in the past.
>
> TMT
>
We run our house on a 12vdc/120vac system. A 2500 watt inverter is
sufficient for our daily loads, the generator picks up the big
occasional loads, as well as some batteyr charging.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Too_Many_Tools

2005-09-17, 1:21 pm

Thanks...that is the type of information that I am looking for.

What do you use the 12vdc side of the system for? Lighting?

TMT

Steve Spence

2005-09-17, 1:21 pm

Too_Many_Tools wrote:
> Thanks...that is the type of information that I am looking for.
>
> What do you use the 12vdc side of the system for? Lighting?
>
> TMT
>

Computer and network equipment, emergency lighting and water. We use a
SHURflo pump connected to rain water system. Also have a 12vdc fridge we
use on occasion.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Marc F Hult

2005-09-17, 2:21 pm

On 17 Sep 2005 07:46:48 -0700, "Too_Many_Tools" <too_many_tools@yahoo.com>
wrote in message <1126968408.243469.263290@g44g2000cwa.googlegroups.com>:

>I think that is the path I may take...in the past I have found that
>since the electronics continue to get "better" it is usually not worth
>trying to design in old stuff....and sometimes "old" means just a few
>years old.
>
>My cost for the UPS equipment I am able to find is nil but one needs to
>factor in long time power usage (idle current), ability to replace it
>when it fails and suitability for the home enviroment. It is a fool who
>designs a system around a surplus component that when it fails, you
>have to toss the whole system. This battery box in question is a
>component that can be useful as my system evolves as it will.
>
>This is one reason for the question of "what voltage" since it is
>apparent that the trend is to different voltages than in the past.
>
>TMT

FWIW, here's what I do (use fixed-spacing font to view ASCII diagram):

Internet
|
Home Automation Control System
|
Genset controller
|
+-----------------+
| |
| |
28vdc NG Genset -->| Switch over------+
|
|
AC line --+--60amp charger/converter -+-- 14vdc batteries ---o 28vdc
| | | |
| +-------+--------+
| |
+--80amp charger/converter -+-- 14vdc batteries ---o 14vdc
| | |
+-------+--------+-------------o vdc 'grnd'

In words:

A bank of deep-cycle lead batteries is series connected to provide 14vdc
(nominal 12vdc) and 28vdc (nominal 24vdc).

Most loads including home automation computers, UPS, and low-voltage light
dimmers are connected to the 28vdc output.

Home control and other devices that can run off 12vdc (security panel, home
automation controllers, video modulators multiplexors, cameras, audio
equipment) are connected to the 14vdc rail.

Devices that need other voltages are supplied via DC-DC converters (eg 5vdv
for microcontrollers, router, switches and so on) or DC-AC inverters (eg
24VAC for HVAC)

The 'lower' (0-14vdc) bank of batteries is recharged and powered by a
UL-listed 80 amp Inteli-power (one "l") charger/supply

http://www.progressivedyn.com/Products.php?ProductID=76

The 'upper bank' (14-28vdc) is recharged and powered by an 60 amp
Inteli-power charger/supply.

Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000 watts.

A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
kick in during power outages that has additional capacity for additional 28vdc
and 120VAC UPS needs. Controller is a Bouchette A120

http://www.bouchette.com/Products/A120C.htm

The choice of 28vdc was driven in large part because this the highest nominal
voltage that meets the requirements of the under-30-volt sections of the
National Electrical code (NEC). A 14vdc system would require conductors
(wires) with twice the cross-sectional area to have the same distribution IR
losses.

This provides isolated, UL-listed, NEC-compliant single-conversion power for
the most/all of critically needed devices including lighting. There is no
interruption whatever if line power goes down because the system is connected
directly to batteries at all times. A power outage simply changes the charging
source from line AC to genset.

The system can be expanded to higher voltages or currents with additional
batteries and chargers. and additional charging sources (eg photovoltaic)
merged.

DC Grounding and maintaining isolation of subsystems that need to have
separate "grounds" is _very_ important and a whole 'nuther topic.

HTH ... Marc
Marc_F_Hult
www.ECOntrol.org

John Beardmore

2005-09-17, 2:21 pm

In message <1126968408.243469.263290@g44g2000cwa.googlegroups.com>,
Too_Many_Tools <too_many_tools@yahoo.com> writes

>I think that is the path I may take...in the past I have found that
>since the electronics continue to get "better" it is usually not worth
>trying to design in old stuff....and sometimes "old" means just a few
>years old.
>
>My cost for the UPS equipment I am able to find is nil but one needs to
>factor in long time power usage (idle current), ability to replace it
>when it fails and suitability for the home enviroment. It is a fool who
>designs a system around a surplus component that when it fails, you
>have to toss the whole system.

I don't know. Any future 'surplus' inverter is likely to be smaller,
cheaper and more powerful than its predecessor, and it's easy enough to
rewire to another battery voltage.

> This battery box in question is a
>component that can be useful as my system evolves as it will.
>
>This is one reason for the question of "what voltage" since it is
>apparent that the trend is to different voltages than in the past.

But not to a single obvious choice of voltage I fear.

Cheers, J/.
--
John Beardmore

Marc F Hult

2005-09-17, 2:21 pm

nospam.clare.nce@sny.der.on.ca

2005-09-17, 2:21 pm

On Sat, 17 Sep 2005 17:27:35 +0100, John Beardmore
<wookie@wookie.demon.co.uk> wrote:

>In message <1126968408.243469.263290@g44g2000cwa.googlegroups.com>,
>Too_Many_Tools <too_many_tools@yahoo.com> writes
>
>
>I don't know. Any future 'surplus' inverter is likely to be smaller,
>cheaper and more powerful than its predecessor, and it's easy enough to
>rewire to another battery voltage.
>
>
>
>But not to a single obvious choice of voltage I fear.
>
>
>Cheers, J/.

Well, with 8 6 volt batteries, the obvious alternatives are 12, 16
(not common at all), 24,32 or 48 volts.36 volts doesn't work out too
well, and 72 and 96 are out of the question. The most common voltages
for low cost inverters and UPS systems are 12 and 24 - with 48 being
used on several large units.
Problem with 48 volt systems is they are generally larger capacity -
and should really have a larger battery pack than you have.

I'd suspect 24 volts is the most likely scenario in your position. (or
wire it as 2 12 volt packs that you can easily switch s/p for 12 or
24)

John Beardmore

2005-09-17, 4:21 pm

In message <hljoi1plfos0bc0t8taia0534ia6qlpi18@4ax.com>,
nospam.clare.nce@sny.der.on.ca writes

>Well, with 8 6 volt batteries, the obvious alternatives are 12, 16
>(not common at all),

You mean 18 ?

> 24,32

32 ?

> or 48 volts.36 volts doesn't work out too
>well, and 72 and 96 are out of the question.

Don't know that they are, though these and higher voltages tend to be
used with wild inputs from wind turbines etc.

> The most common voltages
>for low cost inverters and UPS systems are 12 and 24 - with 48 being
>used on several large units.
>Problem with 48 volt systems is they are generally larger capacity -
>and should really have a larger battery pack than you have.
>
>I'd suspect 24 volts is the most likely scenario in your position. (or
>wire it as 2 12 volt packs that you can easily switch s/p for 12 or
>24)

Not a bad strategy.

J/.
--
John Beardmore

Dan Lanciani

2005-09-17, 5:21 pm

In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:

[big snip]
| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000 watts.
|
| A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
| kick in during power outages that has additional capacity for additional 28vdc
| and 120VAC UPS needs. Controller is a Bouchette A120
|
| http://www.bouchette.com/Products/A120C.htm
|
| The choice of 28vdc was driven in large part because this the highest nominal
| voltage that meets the requirements of the under-30-volt sections of the
| National Electrical code (NEC).

What NEC circuit class does your 28V wiring fall under?

Dan Lanciani
ddl@danlan.*com

Too_Many_Tools

2005-09-17, 6:21 pm

I should mention that I was really surprised that the box relied on
only a passive system (a couple of small vents in the back) to vent
hydrogen.

Is this common with commercial equipment?

The box is stamped with UL and NEC approvals.

TMT

Frank Olson

2005-09-17, 7:21 pm

"Too_Many_Tools" <too_many_tools@yahoo.com> wrote in message
news:1126991094.077828.159950@g14g2000cwa.googlegroups.com...
>I should mention that I was really surprised that the box relied on
> only a passive system (a couple of small vents in the back) to vent
> hydrogen.
>
> Is this common with commercial equipment?
>
> The box is stamped with UL and NEC approvals.
>
> TMT

Sealed lead acid batteries don't vent hydrogen like a standard wet cell
(that only happens if the charger malfunctions). In fact they're designed
to "recycle" it within the battery. Here's a link to a fairly well known
manufacturer.

http://www.gsbattery.com/sla/PDF/SLATechInfo.pdf

GS Batteries has been around for many years. They're the only batteries
Edwards installs in their fire alarm systems (in Canada at least). The Rep
for Western Canada used to show a video of the manufacturing plant in Japan.
The building was huge (covered many acres), and there were only seven people
working there because everything's automated (at least back in 1987). I'm
not entirely sure that most of the processes weren't controlled by earlier
versions of Elk Magic Modules... :-))

John Beardmore

2005-09-17, 7:21 pm

In message <1126991094.077828.159950@g14g2000cwa.googlegroups.com>,
Too_Many_Tools <too_many_tools@yahoo.com> writes

>I should mention that I was really surprised that the box relied on
>only a passive system (a couple of small vents in the back) to vent
>hydrogen.
>
>Is this common with commercial equipment?
>
>The box is stamped with UL and NEC approvals.

How much hydrogen do you think will be evolved ?

Cheers, J/.
--
John Beardmore

Marc F Hult

2005-09-17, 7:21 pm

On 17 Sep 2005 19:18:03 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331582@news1.IPSWITCHS.CMM>:

>In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>,
MFHult@nothydrologistnot.com (Marc F Hult) writes:
>
>[big snip]
>| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000
>|watts.
>|
>| A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
>| kick in during power outages that has additional capacity for additional
>|28vdc
>| and 120VAC UPS needs. Controller is a Bouchette A120
>|
>| http://www.bouchette.com/Products/A120C.htm
>|
>| The choice of 28vdc was driven in large part because this the highest nominal
>| voltage that meets the requirements of the under-30-volt sections of the
>| National Electrical code (NEC).
>
>What NEC circuit class does your 28V wiring fall under?

Depends on which circuit *after* the UL-listed class 2 supply you ask about.

As needed and appropriate, and depending on overcurrent devices and intervening
converters, the subsequent wiring complies with:

Article 411 lighting (isolated; <30 volts/42.4v peak); max 20 amp branch
circuit supply; max 25amp lighting circuit; Class 2 power source; not grounded )

Article 720 ( <50 volts; =>12AWG wiring; Article 240 overcurrent )

Article 725.21 Class 1 ( <30 volts and <1000 volt-amp )

Article 725 Class 2/3 (This is what my 24vdc dimmers operate under)

725.21 A0
Class 1 Power-Limited Circuits. These circuits shall
be supplied from a source that has a rated output of not
more than 30 volts and 1000 volt-amperes.

725.51 Wiring Methods on Supply Side of the Class 2
or Class 3 Power Source. Conductors and equipment on
the supply side of the power source shall be installed in
accordance with the appropriate requirements of Chapters 1
through 4. Transformers or other devices supplied from
electric light or power circuits shall be protected by an
overcurrent device rated not over 20 amperes.

725.41 Power Sources for Class 2 and Class 3 Circuits.
(A) Power Source. The power source for a Class 2 or a
Class 3 circuit shall be as specified in 725.41(A)(1), (2),
(3), (4), or (5):
FPN No. 1: Figure 725.41 illustrates the relationships between
Class 2 or Class 3 power sources, their supply, and
the Class 2 or Class 3 circuits.
FPN No. 2: Table 11(A) and Table 11(B) in Chapter 9
provide the requirements for listed Class 2 and Class 3
power sources.
(1) A listed Class 2 or Class 3 transformer
(2) A listed Class 2 or Class 3 power supply
(3) Other listed equipment marked to identify the Class 2
or Class 3 power source

Comments/corrections/additions welcomed.

... Marc
Marc_F_Hult
www.ECOntrol.org

Marc F Hult

2005-09-17, 8:21 pm

On Sat, 17 Sep 2005 22:49:34 +0100, John Beardmore <wookie@wookie.demon.co.uk>
wrote in message <swJkGVFu9ILDFwI9@wookie.demon.co.uk>:

>In message <1126991094.077828.159950@g14g2000cwa.googlegroups.com>,
>Too_Many_Tools <too_many_tools@yahoo.com> writes
>
>
>How much hydrogen do you think will be evolved ?
>
>
>Cheers, J/.

Depends on how smart the charger is, condition of battery, how quickly you want
to recharge the battery after it has been drained, how deeply you drain cycle
it, how anxious you are to prevent stratification of the electrolyte and
sulfation -- among other things ;-)

If it is a standby systems that is seldom actually used (as opposed to a
diurnally cycled system with eg photovoltaics) the use of a smart charger like
in the url below should keep H2 concentration in even lightly convected air to
below the level of concern for explosion unless the space itself is too small.

http://www.progressivedyn.com/chargewizard_home.html

There are hydrogen sensors one could use for monitoring. My now-dated experience
with them was that they were more trouble than they were worth. Presumably they
have improved.

My qualitative experience on what is "too much hydrogen" is limited to having
one largish battery blow up in my face 20 years ago. It hurt (including pride)
but miraculously I suffered no permanent damage.

Marc
Marc_F_Hult
www.ECOntrol.org

Dan Lanciani

2005-09-17, 8:21 pm

In article <hctoi1tmk224c95nbo2nos0t3m56rkf0rt@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 17 Sep 2005 19:18:03 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| <1331582@news1.IPSWITCHS.CMM>:
|
| >In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>,
| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >
| >[big snip]
| >| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000
| >|watts.
| >|
| >| A Baldor natural gas 28vdc genset has been purchased (not yet installed) to
| >| kick in during power outages that has additional capacity for additional
| >|28vdc
| >| and 120VAC UPS needs. Controller is a Bouchette A120
| >|
| >| http://www.bouchette.com/Products/A120C.htm
| >|
| >| The choice of 28vdc was driven in large part because this the highest nominal
| >| voltage that meets the requirements of the under-30-volt sections of the
| >| National Electrical code (NEC).
| >
| >What NEC circuit class does your 28V wiring fall under?
|
| Depends on which circuit *after* the UL-listed class 2 supply you ask about.

What serves as the class 2 supply?

Dan Lanciani
ddl@danlan.*com

Marc F Hult

2005-09-17, 8:21 pm

On 17 Sep 2005 22:35:17 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331584@news1.IPSWITCHS.CMM>:

>In article <hctoi1tmk224c95nbo2nos0t3m56rkf0rt@4ax.com>,
MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| On 17 Sep 2005 19:18:03 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
>| <1331582@news1.IPSWITCHS.CMM>:
>|
>| >In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>,
>| MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| >
>| >[big snip]
>| >| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000
>| >|watts.
>| >|
>| >| A Baldor natural gas 28vdc genset has been purchased (not yet installed)
to
>| >| kick in during power outages that has additional capacity for additional
>| >|28vdc
>| >| and 120VAC UPS needs. Controller is a Bouchette A120
>| >|
>| >| http://www.bouchette.com/Products/A120C.htm
>| >|
>| >| The choice of 28vdc was driven in large part because this the highest
nominal
>| >| voltage that meets the requirements of the under-30-volt sections of the
>| >| National Electrical code (NEC).
>| >
>| >What NEC circuit class does your 28V wiring fall under?
>|
>| Depends on which circuit *after* the UL-listed class 2 supply you ask about.
>
>What serves as the class 2 supply?
>
> Dan Lanciani
> ddl@danlan.*com

Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
previous post. See

http://www.progressivedyn.com/power_converters.html

I'll try to post some pictures to my web site in the next few days.

On Sat, 17 Sep 2005 16:32:56 GMT, Marc F Hult <MFHult@nothydrologistnot.com>
wrote in message <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>:

>
>The 'lower' (0-14vdc) bank of batteries is recharged and powered by a
>UL-listed 80 amp Inteli-power (one "l") charger/supply
>
>http://www.progressivedyn.com/Products.php?ProductID=76
>
>The 'upper bank' (14-28vdc) is recharged and powered by an 60 amp
>Inteli-power charger/supply.

>Internet
> |
>Home Automation Control System
> |
>Genset controller
> |
> +-----------------+
> | |
> | |
>28vdc NG Genset -->| Switch over------+
> |
> |
>AC line --+--60amp charger/converter -+-- 14vdc batteries ---o 28vdc
> | | | |
> | +-------+--------+
> | |
> +--80amp charger/converter -+-- 14vdc batteries ---o 14vdc
> | | |
> +-------+--------+-------------o vdc 'grnd'
Marc
Marc_F_Hult
www.ECOntrol.org

Steve Spence

2005-09-17, 11:21 pm

Too_Many_Tools wrote:
> I should mention that I was really surprised that the box relied on
> only a passive system (a couple of small vents in the back) to vent
> hydrogen.
>
> Is this common with commercial equipment?
>
> The box is stamped with UL and NEC approvals.
>
> TMT
>

probably sealed batteries, so no hydrogen to vent.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Marc F Hult

2005-09-17, 11:21 pm

On Sat, 17 Sep 2005 22:22:22 GMT, Marc F Hult <MFHult@nothydrologistnot.com>
wrote in message <1n5pi1lebiqh3s3r6lmt0gcoj4lamu213v@4ax.com>:
[color=darkred]
>On Sat, 17 Sep 2005 22:49:34 +0100, John Beardmore <wookie@wookie.demon.co.uk>
>wrote in message <swJkGVFu9ILDFwI9@wookie.demon.co.uk>:
>

Cheers? Now you've got me fretting/thinking again ;-) .

Years ago I built a mobile environmental research lab that carried a couple
hundred cubic feet of H2. The lab was quite air tight and I'd work and sleep in
it during Minnesota winters. The H2 was being continually used for scientific
instrumentation to create a flame so it wasn't immediately discernable whether
some was escaping into the lab atmosphere. The lower explosive limit of H2 is
only about 4% ...

If someone has authoritative information on current best management practices
for hydrogen from small battery banks such as we are discussing, I'd appreciate
knowing. Also reasonable priced H2 sensors. A quick f/google showed me that
they are still an obstacle to progress.

TIA ... Marc
Marc_F_Hult
www.ECOntrol.org

Dan Lanciani

2005-09-18, 12:21 am

In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 17 Sep 2005 22:35:17 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| <1331584@news1.IPSWITCHS.CMM>:
|
| >In article <hctoi1tmk224c95nbo2nos0t3m56rkf0rt@4ax.com>,
| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >| On 17 Sep 2005 19:18:03 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| >| <1331582@news1.IPSWITCHS.CMM>:
| >|
| >| >In article <u5hoi1h9m2oklvuv7gjancbi4rdlp8anbg@4ax.com>,
| >| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >| >
| >| >[big snip]
| >| >| Together they provide nominal 60 amps at 28vdc and 20 amps 14vdc =~2000
| >| >|watts.
| >| >|
| >| >| A Baldor natural gas 28vdc genset has been purchased (not yet installed)
| to
| >| >| kick in during power outages that has additional capacity for additional
| >| >|28vdc
| >| >| and 120VAC UPS needs. Controller is a Bouchette A120
| >| >|
| >| >| http://www.bouchette.com/Products/A120C.htm
| >| >|
| >| >| The choice of 28vdc was driven in large part because this the highest
| nominal
| >| >| voltage that meets the requirements of the under-30-volt sections of the
| >| >| National Electrical code (NEC).
| >| >
| >| >What NEC circuit class does your 28V wiring fall under?
| >|
| >| Depends on which circuit *after* the UL-listed class 2 supply you ask about.
| >
| >What serves as the class 2 supply?
| >
| > Dan Lanciani
| > ddl@danlan.*com
|
|
| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
| previous post. See
|
| http://www.progressivedyn.com/power_converters.html

Interesting. I had no idea that you could get class 2 supplies with such
high power output. Maybe I'll have to reconsider my low-voltage distribution
analysis...

Dan Lanciani
ddl@danlan.*com

Marc F Hult

2005-09-18, 1:21 am

On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331585@news1.IPSWITCHS.CMM>:

>In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>,
MFHult@nothydrologistnot.com (Marc F Hult) writes:

>|
>|
>| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
>| previous post. See
>|
>| http://www.progressivedyn.com/power_converters.html
>
>Interesting. I had no idea that you could get class 2 supplies with such
>high power output. Maybe I'll have to reconsider my low-voltage distribution
>analysis...
>

They have gotten very much cheaper, smaller, cooler, more robust, more powerful
-- and Ul. and ULc. What is not quite what I'd like is efficiency for this
particular family of devices. They are rated at ">80%" at unspecified load. In
real world, this might mean 60% under low load. Course they may just be rating
conservatively.

The RV market is big enough to the create volume needed to avoid niche-market
pricing. This particular design (sold under at least three names) has been
around long enough for the engineering to tested and solid. I imagine RV owners
as a group are not the most gentle on equipment.

IMO, Key here is UL and internal transformer isolation. But I haven't probed to
see whether it is specifically UL for Class 2. I am satisfied that it means
engineering needs.

The other important part of a distributed DC system is use of isolating DC-DC
converters. There are plenty of NOS devices to be had in a variety of Vin and
Vout, nominal telco 48vdc being especially prevalent on the resale market.

I generally assume that all equipment that came with a wall wart and is located
more than ~10m from the primary battery bank should be isolated (again) unless
known otherwise. DC-DC converters also provide the current limiting to 'convert'
the battery into Class 1. The NEC specifically states that a plain old zinc dry
cell is Class 2 (not 1) because the potentially high current capabilities. I
wonder how many door bells of yesteryear, connected with 20AWG bell wire, were
in violation ? ;-)

Marc
Marc_F_Hult
www.ECOntrol.org

Dan Lanciani

2005-09-18, 2:21 am

In article <ehopi1lk9nh29a8u247sbu1o1tt5cm65la@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| <1331585@news1.IPSWITCHS.CMM>:
|
| >In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>,
| MFHult@nothydrologistnot.com (Marc F Hult) writes:
|
| >|
| >|
| >| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
| >| previous post. See
| >|
| >| http://www.progressivedyn.com/power_converters.html
| >
| >Interesting. I had no idea that you could get class 2 supplies with such
| >high power output. Maybe I'll have to reconsider my low-voltage distribution
| >analysis...
| >
|
[...]
| IMO, Key here is UL and internal transformer isolation. But I haven't probed to
| see whether it is specifically UL for Class 2. I am satisfied that it means
| engineering needs.

Hmm. But if it isn't UL listed as a class 2 supply then it can't supply class
2 circuits. Class 2 supplies have some pretty stringent requirements for
current limiting (not just over current protection--source impedance is a
consideration). Last time I checked the most power allowed for a class 2
supply in the lowest voltage range was 100VA. (At higher voltages the power
is reduced disproportionately IIRC.)

Another issue is that even if the supplies are listed as class 2 you can't
interconnect them unless they are also listed for _that_. (721-45(b) in
the 1999 NEC)

| The other important part of a distributed DC system is use of isolating DC-DC
| converters. There are plenty of NOS devices to be had in a variety of Vin and
| Vout, nominal telco 48vdc being especially prevalent on the resale market.
|
| I generally assume that all equipment that came with a wall wart and is located
| more than ~10m from the primary battery bank should be isolated (again) unless
| known otherwise.

I assume that anything that came with a wall wart needs to be isolated
regardless of location unless it has no other external connections.
Sometimes the negative power input is not common with the "common" of
any other connection. Very annoying...

| DC-DC converters also provide the current limiting to 'convert'
| the battery into Class 1.

You probably want to "convert" to class 2, but I don't know if DC-DC
converters are generally listed for that. (If you convert to class 1
then you are stuck with class 1 wiring materials and methods on the
load side, making the whole thing more trouble than running high voltage
to a wall wart.

)

|The NEC specifically states that a plain old zinc dry
| cell is Class 2 (not 1) because the potentially high current capabilities.

It's sort of the other way around. A dry cell (provided it is < 30V and has
<= the capacity of a series string of No. 6 carbon zinc cells) is considered
an inherently limited class 2 power source. That is, the power available from
such batteries is *low* enough to be considered class 2. Any more power and
it would be class 1 (or worse).

|I
| wonder how many door bells of yesteryear, connected with 20AWG bell wire, were
| in violation ? ;-)

Bell circuits have used current-limited class 2 transformers for a long
time (though I don't know when they actually started calling them that).

Dan Lanciani
ddl@danlan.*com

Marc F Hult

2005-09-18, 12:21 pm

On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331587@news1.IPSWITCHS.CMM>:

>In article <ehopi1lk9nh29a8u247sbu1o1tt5cm65la@4ax.com>,
MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
>| <1331585@news1.IPSWITCHS.CMM>:
>|
>| >In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>,
>| MFHult@nothydrologistnot.com (Marc F Hult) writes:
>|
>| >|
>| >|
>| >| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
>| >| previous post. See
>| >|
>| >| http://www.progressivedyn.com/power_converters.html
>| >
>| >Interesting. I had no idea that you could get class 2 supplies with such
>| >high power output. Maybe I'll have to reconsider my low-voltage
distribution
>| >analysis...
>| >
>|
>[...]
>| IMO, Key here is UL and internal transformer isolation. But I haven't probed
to
>| see whether it is specifically UL for Class 2. I am satisfied that it means
>| engineering needs.
>
>Hmm. But if it isn't UL listed as a class 2 supply then it can't supply class
>2 circuits. Class 2 supplies have some pretty stringent requirements for
>current limiting (not just over current protection--source impedance is a
>consideration). Last time I checked the most power allowed for a class 2
>supply in the lowest voltage range was 100VA. (At higher voltages the power
>is reduced disproportionately IIRC.)

Interesting.

Thanks for the clarification about Class 2. I musta had at least NEC Class 2 and
Class I, Division 2 all jumbled up ;-)

It would appear that the listing for the PD91x0 devices is probably UL 458 ("
Chargers or charging functions incorporated into converter or inverters for use
in recreational vehicles and boats, as covered by the Standard for Power
Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and
Marine Crafts").

For home use, they may need to be listed under UL 1012. " These requirements
cover portable, stationary, and fixed power units having an input rating of 600
volts or less, direct- and alternating- current, with at least one output not
marked Class 2, and that are intended to be employed in ordinary locations in
accordance with the National Electrical Code, ANSI/NFPA 70." ) I dunno.

http://search.globalspec.com/engine...ndards/abstract
/24003535340/UL_Standard_for_Safety_Power_Units_Other_Than_Class_2

http://ulstandardsinfonet.ul.com/scopes/1012.html

Previously I identified four sections of the code that seem to pertain:

Article 411 lighting (isolated; <30 volts/42.4v peak); max 20 amp branch
circuit supply; max 25amp lighting circuit; Class 2 power source; not grounded )

Article 720 ( <50 volts; =>12AWG wiring; Article 240 overcurrent )

Article 725.21 Class 1 ( <30 volts and <1000 volt-amp )

Article 725 Class 2 (supplying or active converting <100 watts at =<30VAC or
=<60vdc )

Power for telcomm equipment is yet another set of NEC provisions that may
pertain depending on what it being powered.

Article 411 is not particularly useful because it appears to pertain to a
complete unit that is UL listed as a system. One can buy low voltage wiring
systems as a package that conform to 411 that use bare wires a few inches from a
tall person's head. But if is unclear that one can substitute or fix anything
and still be compliant. Note the "Class 2 power source requirement" .

Article 720 is where I should have indicated that the DC _supply_ to my
low-voltage lighting dimmers fall. As practical matter, one uses conventional (
Sect 1-4 ANSI/NFPA 70) wiring but keeps these conductors out of conduits and
boxes that also contain 120/220 VAC. My DC dimmer panel is about 4 feet from the
PD91x0 supplies so this is easy to do.

Article 725.21 Class 1 (not 2 Thank you ;-) ) would seem to pertain to (in my
case) to:

1) The distribution of power from the centrally-located DC lighting dimmers
(24vdc input, 0-12vdc output) to my commercial track lighting that is UL-listed
for remote transformers.

http://www.ipnlighting.com/faq/linear_faqs.htm

Each dimmer is rated at 250 watts and has its own 20 amp breaker.

2) The distribution of power from the 12vdc supply (tap) of my system (80 x 12
= 960 < 1000v-a) as 725.21 Class 1

So the principal questions would seem to revolve around

1) UL 458 vs UL 1012(?) listing of the PD91x0 charger/supplies

2) Use of Class 2 DC-DC converters such as

http://www.axiomatic.com/24vdc-power-supply.html
http://www.ecnmag.com/article/CA502...01ec51ps616.xml
to provide a Class 2 source from Art 720 distribution

3) Compliance with Art 720 + Art 240, rather than Art 725, if listed Class 2
DC-DC converters are not used.

Power for telcomm equipment is yet another set of NEC provisions that may
pertain depending on what it being powered.

.... Marc
Marc_F_Hult
www.ECOntrol.org

Too_Many_Tools

2005-09-18, 1:21 pm

Oh yes...that answers why no active venting...the batteries were indeed
sealed.

Thanks for answering that little mystery.

TMT

Too_Many_Tools

2005-09-18, 1:21 pm

A question for the group...

This battery box I have has its batteries arranged in two groups of
four with one group mounted above the other group.

How have you organized your battery box?

Are they all laid out horizontally, stacked on shelves, mounted in roll
out drawers or what? I am looking for ideas for efficient layout of the
batteries and this battery box is one approach. It seems to work well
except for the fact that the bottom layer of batteries would be
difficult to access for maintainence.

TMT

Marc F Hult

2005-09-18, 1:21 pm

On Sun, 18 Sep 2005 15:04:00 GMT, Marc F Hult <MFHult@nothydrologistnot.com>
wrote in message <jlpqi1pug6c0m8uiqalsq7hjeau43aqu44@4ax.com>:

In ASCII, continuing from previous diagram:

28vdc -+->Circuit Breaker--->Dimmer module--->12vdc track UL w/remote xfmr
| (Art. 720 + 240) (Art 725.21 Class 1)
|
+->Circuit Breaker -------------> devices
| (Art. 720 + 240)
|
+----> DC-DC converter ----+---> device
(Art.725 Class 2) +---> device ground

14vdc -+----> DC-DC converter ----+---> device
| (Art.725 Class 2) +---> device ground
|
+----------------------------> device(s)
(Art 725.21 Class 1)

0 ----------------------------------> ground
(Art. 720 and 725 class 1)

Not shown are low-voltage outdoor lighting or telecomm.

Marc
Marc_F_Hult
www.ECOntrol.org

nospam.clare.nce@sny.der.on.ca

2005-09-18, 2:21 pm

On Sat, 17 Sep 2005 19:57:25 +0100, John Beardmore
<wookie@wookie.demon.co.uk> wrote:

>In message <hljoi1plfos0bc0t8taia0534ia6qlpi18@4ax.com>,
>nospam.clare.nce@sny.der.on.ca writes
>
>
>You mean 18 ?
Caught me
>
>
>
>32 ?
Yes, you caught me- 36 works fine
>
>
>
>Don't know that they are, though these and higher voltages tend to be
>used with wild inputs from wind turbines etc.

How will you get either 72 or 96 volts with only 8 X 6 volt batteries
- Maximum voltage POSSIBLE with this battery pack is 48.
>
>
>
>Not a bad strategy.
>
>
>J/.

nospam.clare.nce@sny.der.on.ca

2005-09-18, 2:21 pm

On Sat, 17 Sep 2005 22:22:22 GMT, Marc F Hult
<MFHult@nothydrologistnot.com> wrote:

..

With AGM batteries it more the heat than the hydrogen they are worried
about.[color=darkred]
>
>
>Depends on how smart the charger is, condition of battery, how quickly you want
>to recharge the battery after it has been drained, how deeply you drain cycle
>it, how anxious you are to prevent stratification of the electrolyte and
>sulfation -- among other things ;-)

Stratification of acid in AGM batteries is, AFAIK, not only not an
issue, but not possible.
>

Steve Spence

2005-09-18, 3:21 pm

Too_Many_Tools wrote:
> A question for the group...
>
> This battery box I have has its batteries arranged in two groups of
> four with one group mounted above the other group.
>
> How have you organized your battery box?
>
> Are they all laid out horizontally, stacked on shelves, mounted in roll
> out drawers or what? I am looking for ideas for efficient layout of the
> batteries and this battery box is one approach. It seems to work well
> except for the fact that the bottom layer of batteries would be
> difficult to access for maintainence.
>
> TMT
>

Mine are 2 deep, three wide in a single layer.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Solar Flare

2005-09-19, 12:21 am

Stadium seating is generally a good access for maintenance.

"Too_Many_Tools" <too_many_tools@yahoo.com> wrote in message
news:1127058845.938019.64920@g49g2000cwa.googlegroups.com...
A question for the group...

This battery box I have has its batteries arranged in two groups of
four with one group mounted above the other group.

How have you organized your battery box?

Are they all laid out horizontally, stacked on shelves, mounted in roll
out drawers or what? I am looking for ideas for efficient layout of the
batteries and this battery box is one approach. It seems to work well
except for the fact that the bottom layer of batteries would be
difficult to access for maintainence.

TMT

Dan Lanciani

2005-09-19, 6:21 am

In article <jlpqi1pug6c0m8uiqalsq7hjeau43aqu44@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:
| On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| <1331587@news1.IPSWITCHS.CMM>:
|
| >In article <ehopi1lk9nh29a8u247sbu1o1tt5cm65la@4ax.com>,
| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
| >| <1331585@news1.IPSWITCHS.CMM>:
| >|
| >| >In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>,
| >| MFHult@nothydrologistnot.com (Marc F Hult) writes:
| >|
| >| >|
| >| >|
| >| >| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in my
| >| >| previous post. See
| >| >|
| >| >| http://www.progressivedyn.com/power_converters.html
| >| >
| >| >Interesting. I had no idea that you could get class 2 supplies with such
| >| >high power output. Maybe I'll have to reconsider my low-voltage
| distribution
| >| >analysis...
| >| >
| >|
| >[...]
| >| IMO, Key here is UL and internal transformer isolation. But I haven't probed
| to
| >| see whether it is specifically UL for Class 2. I am satisfied that it means
| >| engineering needs.
| >
| >Hmm. But if it isn't UL listed as a class 2 supply then it can't supply class
| >2 circuits. Class 2 supplies have some pretty stringent requirements for
| >current limiting (not just over current protection--source impedance is a
| >consideration). Last time I checked the most power allowed for a class 2
| >supply in the lowest voltage range was 100VA. (At higher voltages the power
| >is reduced disproportionately IIRC.)
|
| Interesting.
|
| Thanks for the clarification about Class 2. I musta had at least NEC Class 2 and
| Class I, Division 2 all jumbled up ;-)

As in Class I hazardous locations?

| It would appear that the listing for the PD91x0 devices is probably UL 458 ("
| Chargers or charging functions incorporated into converter or inverters for use
| in recreational vehicles and boats, as covered by the Standard for Power
| Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and
| Marine Crafts").
|
| For home use, they may need to be listed under UL 1012. " These requirements
| cover portable, stationary, and fixed power units having an input rating of 600
| volts or less, direct- and alternating- current, with at least one output not
| marked Class 2, and that are intended to be employed in ordinary locations in
| accordance with the National Electrical Code, ANSI/NFPA 70." ) I dunno.

Perhaps. However, I just looked at the hookup instructions and it appears
that the outputs are directly paralleled with the battery bank, i.e., whatever
over-current protection the devices offer does not actually protect the load
side. That suggests that no matter the listing the output is going to have to
be treated like the output of any other battery bank which can deliver very
high current, requiring, e.g., (expensive) class T fuses. And of course, the
wiring at that point isn't even class 1. (I used to think that it could be
class 1 subpar (b) which goes to 600V with no power limitations, but that's
for signaling/control only...)

| Previously I identified four sections of the code that seem to pertain:
|
| Article 411 lighting (isolated; <30 volts/42.4v peak); max 20 amp branch
| circuit supply; max 25amp lighting circuit; Class 2 power source; not grounded )
|
| Article 720 ( <50 volts; =>12AWG wiring; Article 240 overcurrent )
|
| Article 725.21 Class 1 ( <30 volts and <1000 volt-amp )
|
| Article 725 Class 2 (supplying or active converting <100 watts at =<30VAC or
| =<60vdc )
|
| Power for telcomm equipment is yet another set of NEC provisions that may
| pertain depending on what it being powered.
|
| Article 411 is not particularly useful because it appears to pertain to a
| complete unit that is UL listed as a system. One can buy low voltage wiring
| systems as a package that conform to 411 that use bare wires a few inches from a
| tall person's head. But if is unclear that one can substitute or fix anything
| and still be compliant. Note the "Class 2 power source requirement" .

411 didn't used to (as of the 1999 NEC) require a class 2 supply and was
(according to the notes) intended to cover both interior and exterior
(landscape) lighting. The wiring could be extended through/in a wall but
only by using Chapter 3 materials and methods. So even then it didn't
really buy you much. If they have added a genuine class 2 supply requirement
I would think that many of the existing landscape lighting transformers are
now out of spec since even the multi-output ones typically exceeded 100VA on
each output. It may be that there is now a specific (and different) type
of class 2 listing for such supplies that makes this all work out. There
is an unfortunate trend in this respect to make listings extremely application-
specific, thus thwarting non-standard or unanticipated custom assemblies.

| Article 720 is where I should have indicated that the DC _supply_ to my
| low-voltage lighting dimmers fall. As practical matter, one uses conventional (
| Sect 1-4 ANSI/NFPA 70) wiring but keeps these conductors out of conduits and
| boxes that also contain 120/220 VAC. My DC dimmer panel is about 4 feet from the
| PD91x0 supplies so this is easy to do.
|
| Article 725.21 Class 1 (not 2 Thank you ;-) ) would seem to pertain to (in my
| case) to:
|
| 1) The distribution of power from the centrally-located DC lighting dimmers
| (24vdc input, 0-12vdc output) to my commercial track lighting that is UL-listed
| for remote transformers.
|
| http://www.ipnlighting.com/faq/linear_faqs.htm
|
| Each dimmer is rated at 250 watts and has its own 20 amp breaker.
|
| 2) The distribution of power from the 12vdc supply (tap) of my system (80 x 12
| = 960 < 1000v-a) as 725.21 Class 1

Here's the problem I had when I looked at the whole low-voltage DC distribution
idea a while back. Whether you classify your circuits under 720 or 725's
class 1 you still have to use the same Chapter 3 materials and methods that
you would use for line voltage circuits. Plus you have to keep the two
(or maybe all three) separate. Plus you have to deal with non-standard
(and thus more expensive) ancillary components like DC-rated switches and
fuses. Plus you have the inherent loss disadvantages of low voltage. As
far as I can tell, the only thing you gain under class 1 is the ability to
use No. 16 and 18 conductors, not that I'd want to. Am I missing something?

Dan Lanciani
ddl@danlan.*com

Marc F Hult

2005-09-19, 11:21 am

On 19 Sep 2005 08:23:57 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331589@news1.IPSWITCHS.CMM>:

>In article <jlpqi1pug6c0m8uiqalsq7hjeau43aqu44@4ax.com>,
MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| On 18 Sep 2005 05:13:37 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
>| <1331587@news1.IPSWITCHS.CMM>:
>|
>| >In article <ehopi1lk9nh29a8u247sbu1o1tt5cm65la@4ax.com>,
>| MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| >| On 18 Sep 2005 02:52:12 GMT, ddl@danlan.*com (Dan Lanciani) wrote in
message
>| >| <1331585@news1.IPSWITCHS.CMM>:
>| >|
>| >| >In article <as8pi1da45o1psehe0s983ql7439j8k3ek@4ax.com>,
>| >| MFHult@nothydrologistnot.com (Marc F Hult) writes:
>| >|
>| >| >|
>| >| >|
>| >| >| Inteli-Power PD9180 and PD9160 (now Progressive Dynamics) as I wrote in
my
>| >| >| previous post. See
>| >| >|
>| >| >| http://www.progressivedyn.com/power_converters.html
>| >| >
>| >| >Interesting. I had no idea that you could get class 2 supplies with such
>| >| >high power output. Maybe I'll have to reconsider my low-voltage
>| distribution
>| >| >analysis...
>| >| >
>| >|
>| >[...]
>| >| IMO, Key here is UL and internal transformer isolation. But I haven't
probed
>| to
>| >| see whether it is specifically UL for Class 2. I am satisfied that it
means
>| >| engineering needs.
>| >
>| >Hmm. But if it isn't UL listed as a class 2 supply then it can't supply
class
>| >2 circuits. Class 2 supplies have some pretty stringent requirements for
>| >current limiting (not just over current protection--source impedance is a
>| >consideration). Last time I checked the most power allowed for a class 2
>| >supply in the lowest voltage range was 100VA. (At higher voltages the power
>| >is reduced disproportionately IIRC.)
>|
>| Interesting.
>|
>| Thanks for the clarification about Class 2. I musta had at least NEC Class 2
and
>| Class I, Division 2 all jumbled up ;-)
>
>As in Class I hazardous locations?

and even maybe even NCAA Division 1 and 2 ;-)
>
>| It would appear that the listing for the PD91x0 devices is probably UL 458 ("
>| Chargers or charging functions incorporated into converter or inverters for
use
>| in recreational vehicles and boats, as covered by the Standard for Power
>| Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles
and
>| Marine Crafts").
>|
>| For home use, they may need to be listed under UL 1012. " These requirements
>| cover portable, stationary, and fixed power units having an input rating of
600
>| volts or less, direct- and alternating- current, with at least one output not
>| marked Class 2, and that are intended to be employed in ordinary locations in
>| accordance with the National Electrical Code, ANSI/NFPA 70." ) I dunno.
>
>Perhaps. However, I just looked at the hookup instructions and it appears
>that the outputs are directly paralleled with the battery bank, i.e., whatever
>over-current protection the devices offer does not actually protect the load
>side. That suggests that no matter the listing the output is going to have to
>be treated like the output of any other battery bank which can deliver very
>high current, requiring, e.g., (expensive) class T fuses. And of course, the
>wiring at that point isn't even class 1. (I used to think that it could be
>class 1 subpar (b) which goes to 600V with no power limitations, but that's
>for signaling/control only...)

Yes. See the ASCII circuit diagram in my previous post and at the end of this
one. which I think makes this clear. Over-current protection is included.

Where do I find out about class T fuses ? Searching the 2005 draft NEC came up
blank. Why do I need them? Plain old Square D QO circuit breakers are UL'd to
60vdc.

>| Previously I identified four sections of the code that seem to pertain:
>|
>| Article 411 lighting (isolated; <30 volts/42.4v peak); max 20 amp branch
>| circuit supply; max 25amp lighting circuit; Class 2 power source; not
grounded )
>|
>| Article 720 ( <50 volts; =>12AWG wiring; Article 240 overcurrent )
>|
>| Article 725.21 Class 1 ( <30 volts and <1000 volt-amp )
>|
>| Article 725 Class 2 (supplying or active converting <100 watts at =<30VAC or
>| =<60vdc )
>|
>| Power for telcomm equipment is yet another set of NEC provisions that may
>| pertain depending on what it being powered.
>|
>| Article 411 is not particularly useful because it appears to pertain to a
>| complete unit that is UL listed as a system. One can buy low voltage wiring
>| systems as a package that conform to 411 that use bare wires a few inches
from a
>| tall person's head. But if is unclear that one can substitute or fix anything
>| and still be compliant. Note the "Class 2 power source requirement" .
>
>411 didn't used to (as of the 1999 NEC) require a class 2 supply and was
>(according to the notes) intended to cover both interior and exterior
>(landscape) lighting. The wiring could be extended through/in a wall but
>only by using Chapter 3 materials and methods. So even then it didn't
>really buy you much. If they have added a genuine class 2 supply requirement
>I would think that many of the existing landscape lighting transformers are
>now out of spec since even the multi-output ones typically exceeded 100VA on
>each output. It may be that there is now a specific (and different) type
>of class 2 listing for such supplies that makes this all work out. There
>is an unfortunate trend in this respect to make listings extremely application-
>specific, thus thwarting non-standard or unanticipated custom assemblies.

Right. ABIK, it has changed and become more restrictive/ less useful. That was
my point.

Outdoor wiring low-voltage wiring was separated in the 2002(?). I haven't
pursued what the draft 2005 has to say. but I didn't stumble across anything
that clarified how to get from one t'other or made life easier.

>| Article 720 is where I should have indicated that the DC _supply_ to my
>| low-voltage lighting dimmers fall. As practical matter, one uses conventional
(
>| Sect 1-4 ANSI/NFPA 70) wiring but keeps these conductors out of conduits and
>| boxes that also contain 120/220 VAC. My DC dimmer panel is about 4 feet from
the
>| PD91x0 supplies so this is easy to do.
>|
>| Article 725.21 Class 1 (not 2 Thank you ;-) ) would seem to pertain to (in
my
>| case) to:
>|
>| 1) The distribution of power from the centrally-located DC lighting dimmers
>| (24vdc input, 0-12vdc output) to my commercial track lighting that is
UL-listed
>| for remote transformers.
>|
>| http://www.ipnlighting.com/faq/linear_faqs.htm
>|
>| Each dimmer is rated at 250 watts and has its own 20 amp breaker.
>|
>| 2) The distribution of power from the 12vdc supply (tap) of my system (80 x
12
>| = 960 < 1000v-a) as 725.21 Class 1
>
>Here's the problem I had when I looked at the whole low-voltage DC distribution
>idea a while back. Whether you classify your circuits under 720 or 725's
>class 1 you still have to use the same Chapter 3 materials and methods that
>you would use for line voltage circuits. Plus you have to keep the two
>(or maybe all three) separate. Plus you have to deal with non-standard
>(and thus more expensive) ancillary components like DC-rated switches and
>fuses. Plus you have the inherent loss disadvantages of low voltage. As
>far as I can tell, the only thing you gain under class 1 is the ability to
>use No. 16 and 18 conductors, not that I'd want to. Am I missing something?
>

Yes and maybe not :-)

Yes, from the perspective that you are analyzing the benefits as if the
installation is something to be commercialized -- which it is not. There is no
reason why a personal endeavor ("hobby") has to be practical, or cost effective.
Most of what I see folks doing in comp.home.automation (and perhaps the
cross-posted NGs too) would not meet those criteria. Perhaps we need to start a
rec.home.automation ;-)

Yes, from social reality that in a system with multiple, distributed components
that require electrical power, the conventional approach of providing that
energy with Class 2 wallwarts quickly becomes untenable. Spousal factor -- the
answer to "Can I put three _more_ wall warts over here so that the open-close
and tilt drapery motors and the controller can be powered?" is "No". So what
to do ? One part of the answer is distributed DC power in my case.

Yes, examining the assertion that 120VAC is always standard and low-voltage is
non-standard. To the extent that many of my objectives stem from, and are
ultimately directed at environmental monitoring, 120 AC is very much the
non-standard, not low-voltage. When was the last time you saw a AC-powered pH or
conductance meter? Or weather station? Or sampling pump, or ... My backyard is
750 feet of river front that we own and I monitor.

Yes, from the standpoint that you see "keeping lines separate" as a negative.
We separate AC lines one from another too. Why is this a problem? Why is it not
a design advantage to have independent systems? I can rip everything I've
installed out and the house and household would go on jist fine, albeit with
diminution of smart/automation functionality and emergency and aesthetic aspects
of lighting.

Yes, from the difference that you see having to use Chapter 3 materials as a
problem, whereas I see it as the cheapest way to get materials in many cases
anyway. The power of Home Depotizing as it were ..

Yes, recognizing that I already have a large supply of components for DIY.
Sometimes I build things just to convert "parts" into "devices" (in the spirit
of rec.home.automation ;-)

Yes, from the fact that the "inherent loss disadvantages of low voltage" is
eliminated completely by proportional increase in the cross-sectional areas of
conductors. There are, of course, advantages to higher voltages. We converted
our house in Spain from 110 to 220 3-phase which made conductors embedded in
solid masonry walls much more useful. But that is not the situation in my US
home. I am installing new conductors, and don't have to retrofit. The house is
184 years old and this is at least the fifth energy/lighting infrastructure
(Candle/lamp; coal gas lighting; knob and tube electrical; 1983 Romex
remodeling; 21st century HA )

And maybe *not* ;-) because you have excellent analytical abilities and apply
them diligently to a confusing set of facts, boundary conditions, circumstances
and regulations in a way that is very helpful to others (too).

I _greatly_ appreciate you helpful comments. You've helped to clarify, organize
and correct much.

Regards ... Marc
Marc_F_Hult
www.ECOntrol.org

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

On Sun, 18 Sep 2005 15:04:00 GMT, Marc F Hult <MFHult@nothydrologistnot.com>
wrote in message <jlpqi1pug6c0m8uiqalsq7hjeau43aqu44@4ax.com>:

In ASCII, continuing from previous diagram:

28vdc -+->Circuit Breaker--->Dimmer module--->12vdc track UL w/remote xfmr
| (Art. 720 + 240) (Art 725.21 Class 1)
|
+->Circuit Breaker -------------> devices
| (Art. 720 + 240)
|
+----> DC-DC converter ----+---> device
(Art.725 Class 2) +---> device ground

14vdc -+----> DC-DC converter ----+---> device
| (Art.725 Class 2) +---> device ground
|
+----------------------------> device(s)
(Art 725.21 Class 1)

0 ----------------------------------> ground
(Art. 720 and 725 class 1)

Not shown are low-voltage outdoor lighting or telecomm.

Dan Lanciani

2005-09-21, 3:21 am

In article <7qcti1pqcg7enml3oijr9jtvao4rb0984f@4ax.com>, MFHult@nothydrologistnot.com (Marc F Hult) writes:

[this is getting long, so big snip...]

| I wrote:

| >Perhaps. However, I just looked at the hookup instructions and it appears
| >that the outputs are directly paralleled with the battery bank, i.e., whatever
| >over-current protection the devices offer does not actually protect the load
| >side. That suggests that no matter the listing the output is going to have to
| >be treated like the output of any other battery bank which can deliver very
| >high current, requiring, e.g., (expensive) class T fuses. And of course, the
| >wiring at that point isn't even class 1. (I used to think that it could be
| >class 1 subpar (b) which goes to 600V with no power limitations, but that's
| >for signaling/control only...)
|
| Yes. See the ASCII circuit diagram in my previous post and at the end of this
| one. which I think makes this clear. Over-current protection is included.

Yes, you were clear. I was confused by the description on the manufacturer's
site. With all the talk of sophisticated over-current detection I thought the
supply had to interpose some electronics between the battery string and the
output. I guess the protection is just for the wires to the battery.

In
case you care, I'm pretty sure that there do exist supplies that work the way
I thought these work.

| Where do I find out about class T fuses ?

A Google search seems to turn up quite a few hits. One thing I noticed is
that they aren't as absurdly expensive as I remembered...

| Searching the 2005 draft NEC came up
| blank. Why do I need them?

To be honest, I'm not sure you do. This came up some years ago when I
added a remote battery string to a UPS. To my annoyance I found that while
inexpensive 100A automotive fuses could be used for similar applications in
cars, boats, mobile homes, and even internally to said UPS and its packaged
expansion batteries, I had to use a class T fuse because I was running the
circuit in a building. This might have been a local issue and/or I might have
overreacted to some of the requirements. After getting the correct fuse I sort
of stopped looking for additional problems because, well, the box I was using
wasn't a listed battery enclosure and the UPS wasn't actually listed for
connection to anything but their packaged expansion batteries (though at least
the string I used fell within the allowable range of capacities) and so on...

| Plain old Square D QO circuit breakers are UL'd to
| 60vdc.

As I recall, a circuit breaker with the required DC arc interrupting capacity
(20kA?) and response time was even more expensive than the fuses. But since
a lot of this is listing politics rather than genuine engineering it's
certainly possible that a commodity device would have been acceptable and
I just missed it.

| >If they have added a genuine class 2 supply requirement
| >I would think that many of the existing landscape lighting transformers are
| >now out of spec since even the multi-output ones typically exceeded 100VA on
| >each output. It may be that there is now a specific (and different) type
| >of class 2 listing for such supplies that makes this all work out. There
| >is an unfortunate trend in this respect to make listings extremely application-
| >specific, thus thwarting non-standard or unanticipated custom assemblies.
|
| Right. ABIK, it has changed and become more restrictive/ less useful. That was
| my point.
|
| Outdoor wiring low-voltage wiring was separated in the 2002(?). I haven't
| pursued what the draft 2005 has to say. but I didn't stumble across anything
| that clarified how to get from one t'other or made life easier.

I just checked the Juno Flex 12 system for which I happen to have a catalog.
It's one of those exposed-conductor indoor low-voltage track systems. The
transformers go to 600VA per circuit, so I think even indoor systems are
going to have a problem with a class 2 supply requirement. Unless those
were never under 411 to begin with (like your tracks?).

| >Here's the problem I had when I looked at the whole low-voltage DC distribution
| >idea a while back. Whether you classify your circuits under 720 or 725's
| >class 1 you still have to use the same Chapter 3 materials and methods that
| >you would use for line voltage circuits. Plus you have to keep the two
| >(or maybe all three) separate. Plus you have to deal with non-standard
| >(and thus more expensive) ancillary components like DC-rated switches and
| >fuses. Plus you have the inherent loss disadvantages of low voltage. As
| >far as I can tell, the only thing you gain under class 1 is the ability to
| >use No. 16 and 18 conductors, not that I'd want to. Am I missing something?
| >
|
| Yes and maybe not :-)
|
| Yes, from the perspective that you are analyzing the benefits as if the
| installation is something to be commercialized -- which it is not.

I was really trying to frame some simpler questions. What is it that you
are allowed to do by remaining < 30V that you would not be allowed to do if
you used, say, 48V? Similarly for using DC instead of AC.

| Yes, from social reality that in a system with multiple, distributed components
| that require electrical power, the conventional approach of providing that
| energy with Class 2 wallwarts quickly becomes untenable. Spousal factor -- the
| answer to "Can I put three _more_ wall warts over here so that the open-close
| and tilt drapery motors and the controller can be powered?" is "No". So what
| to do ? One part of the answer is distributed DC power in my case.

Don't the DC/DC converters take up about as much space as the wall warts
they replace? Or do you have enough consumer devices that require neither
voltage conversion nor isolation nor class 2 current limitation that you come
out ahead?

Dan Lanciani
ddl@danlan.*com

Marc F Hult

2005-09-25, 1:21 pm

On 21 Sep 2005 05:09:19 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331592@news1.IPSWITCHS.CMM>:

>I was really trying to frame some simpler questions. What is it that you
>are allowed to do by remaining < 30V that you would not be allowed to do if
>you used, say, 48V? Similarly for using DC instead of AC.

IOW, get back to the Q&A that might have transfer value to other folks.
Thank you ;-)

Allow me to assert that, side for legacy requirements for some thermostats
and HVAC controls, nearly all home automation/control/measurement electrical
power needs are intrinsically DC. (Air conditioning, heating, large motors
etc are beyond our scope here.)

The system I've described and shown in schematics consists in building blocks
in increments of nominal 12vdc (~13.8 vdc. One can easily add additional
voltages in series on _top_ of the 0-12-24vdc voltage, 80/60 amp
configuration.

So I could create a 1.25 amp 48vdc supply with two 1.25amp 13.8vdc Powersonic
wall-wart chargers and two 7AH sealed lead cells (the most cost-effective
size) that I have on hand and move around for various projects. I have been
using this particular combination from this supplier for isolated power
supplies for environmental monitoring for at least 20 years.

This would provide a system with 0-12-24-36-48vdc at 80/60/1.25/1.25 amps

48vdc just doesn't happen to be needed in my case right now, which (based on
the devices I have) _does_ need ~40 amps at nominal 24vdc to power the DC
dimmers that I happen to use. Requirements of other folks will vary. Point is
that the approach is modular, and one can move things around as needs change,
which in a experimental/hobbyist environment, they inevitably do.

Recognize that if the battery bank weren't there, and aside from the
specific listing issue, the 80-amp 12vdc "tap" is Class 1-compliant so one
could partially "de-build" to reach a particular code goal/requirement should
it come to that.

Using a 40 amp instead of 60amp charger/supply would make the 24vdc tap also
Class 1 (same provisos).

>Don't the DC/DC converters take up about as much space as the wall warts
>they replace?

No, in part because the DC-DC converters can be internal to the devices they
power. Compare the hodge-potch of wall-warts, power strips, surge protectors,
and local UPS's that conventionally are used to power a pc and associated
accoutrements with these:

http://www.mini-box.com/s.nl/sc.8/c.../it.A/id.356/.f
http://www.mini-box.com/s.nl/sc.8/c.../it.A/id.300/.f
(the 12vdc on the latter is pass-through, not regulated.
http://cgi.ebay.com/ws/eBayISAPI.dl...rd=1&sspagename
=STRK%3AMEWN%3AIT&rd=1

Which, *inside* an (eg) low-power PC such as VIA EPIA is smaller, more
energy efficient, has fewer connections to fail, and has longer battery
backup among other things.

A standard/conventional hermaphroditic connector for DC connectors are the
Anderson Powerpole series

http://www.andersonpower.com/index.html
which have been adopted by hams as informal quasi standard for Radio Amateur
Civil Emergency Service (RACES) among others

Purchased inexpensively here:

http://www.dcpwr.com/products/produ...SID=b2fc5d42026
3007049701b9f1764ba4d

And recognize -- importantly! -- that the short back-up time on under-desk
UP's don't actually solve *anything* if the PC is supposed to stay up
permanently which is often the case in HA applications. So the conventional
under-desk AC-based tangled jumble fails and the almost invisible, internal
DC solution elegantly and dependably meets the needs.

Depending on the specific CPU requirements (part of this approach involves
getting real with what we actually need in terms of computational horsepower)
sufficient 5vdc and(or) 12vdc power may be available from the same DC-DC
converter to supply a router or other gizmo. If not, add another DC-DC
converter, perhaps within the same case, but certainly not on the wall or on
an AC power strip.

>Or do you have enough consumer devices that require neither
>voltage conversion nor isolation nor class 2 current limitation that you
>come out ahead?

I think that you are asking whether I use devices that can use unregulated
nominal 12vdc or 24vdc. Yes. 12vdc devices abound. And this is a factor in my
purchasing decisions. It also prompts me to take the covers off devices to
see what their internal power supplies _really_ need.

.... Marc
Marc_F_Hult
www.ECOntrol.org

Marc F Hult

2005-09-25, 1:21 pm

On 21 Sep 2005 05:09:19 GMT, ddl@danlan.*com (Dan Lanciani) wrote in message
<1331592@news1.IPSWITCHS.CMM>:

>
>I was really trying to frame some simpler questions. What is it that you
>are allowed to do by remaining < 30V that you would not be allowed to do if
>you used, say, 48V? Similarly for using DC instead of AC.

Let me tackle the 'AC' part here.

(We need to stick to comparing pomes (as in apples to pears) so large diesel
generators and other solutions beyond the modest ones previously implied are
beyond the scope of the solutions to be discussed here.)

I've recently discussed the aesthetic problem of "wall acne" in a thread in
comp.home.automation, so won't repeat that in this thread which is
cross-posted. Let it suffice that there are advantages to low voltage
distribution that are unrelated to the need for uninterrupted power. It is
the need for UPS that I address here.

Starting from the design objective of making power available ad infinitum,
not just for a few minutes to (eg) allow a computer to shut down. This
(necessarily, methinks) results in a _central_ UPS system the power from
which must be distributed as either DC or AC.

The DC supplies I've described provide about (60 x 14 + 80 x 14) =~ 2000
watts . Not coincidentally this is about what 15 amp (1800 watt) and 20 amp
(2400 watt) AC circuits can provide.

Noting that in the US, the National Electrical Code prohibits supplying a
(eg) a conventional wall outlet with less than a 15 amp source, it follows
that an AC UPS with the same capacity as the DC system I described must be on
a _single_ circuit There can be mo overcurrent protection between the panel
and the outlet less than 15 amps.

So in a NEC-compliant 15-20 amp distributed 120vac UPS wiring system, *every*
outlet goes dead if the trip point is exceeded.

Summary:

1) After putting all the most important devices that should never be allowed
to go dead, a NEC-compliant AC system is vulnerable to someone plugging in a
vacuum cleaner during Saturday house cleaning, or to a space heater plugged
in during an emergency and shutting everything down. This is a recipe for
certain failure in my opinion. With the DC distribution system I've
described, over-voltatge protection can be used _ab_ libitum_ (although not
necessarily as effectively as desired -- 'nuther topic ;-)

2) Elsewhere in this thread, Dan correctly notes that the DC system described
requires running new/different wires. How does having power from a single ~
2000 watt UPS system distributed throughout the house obviate the need to
have new/different wires? As best I know, it doesn't.

3) From the efficiency standpoint, DC distribution also has the advantage
when efficiency is most needed, namely when running from batteries. In a DC
distributed system, the power used by (eg) PC goes through exactly one DC-DC
conversion (battery-> DC-DC converter inside PC). In a AC distributed
system, there are at least twice as many conversions with attendant decrease
in overall efficiency of battery utilization (battery--> DC_AC UPS -->
AC_DC_DC converter in computer).

Marc
Marc_F_Hult
www.ECOntrol.com

Marc F Hult

2005-09-25, 2:21 pm

On Sun, 25 Sep 2005 16:01:18 GMT, Marc F Hult <MFHult@nothydrologistnot.com>
wrote in message <mdidj1p9g00kejd952vufeqrq3k1jvho6c@4ax.com>:
> How does having power from a single ~
>2000 watt UPS system distributed throughout the house obviate the need to
^
AC

.... Marc
Marc_F_Hult
www.ECOntrol.org

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